[Diffusion] Register runtime cache for direct DLO H2D

Avoid recurrent mmap-to-pinned packing in no-AllGather DLO by registering transform-complete runtime-cache mappings under an explicit per-worker budget. Copy mapped tensors directly into the rotating device buffers while preserving bounded-staging fallback and ordered shutdown cleanup.

Signed-off-by: Hongsheng Liu <liuhongsheng4@huawei.com>

tests/entrypoints/test_async_omni_diffusion_config.py

@@ -333,6 +333,8 @@ def test_serve_cli_forwards_distributed_offload_residency():
             "/var/cache/vllm-omni-dlo",
             "--dlo-runtime-cache-lock-timeout",
             "30",
+            "--dlo-runtime-cache-pin-limit-gib",
+            "80",
             "--dlo-resident-layers",
             "20",
         ]
@@ -347,12 +349,14 @@ def test_serve_cli_forwards_distributed_offload_residency():
     assert args.dlo_enable_runtime_cache is True
     assert args.dlo_runtime_cache_dir == "/var/cache/vllm-omni-dlo"
     assert args.dlo_runtime_cache_lock_timeout == 30
+    assert args.dlo_runtime_cache_pin_limit_gib == 80
     assert args.dlo_resident_layers == 20
     assert engine_args["enable_distributed_layerwise_offload"] is True
     assert engine_args["dlo_use_allgather"] is False
     assert engine_args["dlo_enable_runtime_cache"] is True
     assert engine_args["dlo_runtime_cache_dir"] == "/var/cache/vllm-omni-dlo"
     assert engine_args["dlo_runtime_cache_lock_timeout"] == 30
+    assert engine_args["dlo_runtime_cache_pin_limit_gib"] == 80
     assert engine_args["dlo_resident_layers"] == 20